Big enough ones can make quite a bang but never heard of anyone being killed by one though. Blown ear drums.
Are you sure about that, because the stories that are starting to come out from people who were there are saying something different, like security guards turning people away from the lobby seconds before an explosion etc (Daily Mail report) so with no verified story yet it's a bit odd to claim you know whats happened isn't it?
Not really as depending on where you are in the crowd, you'll see things different from being closer to the event... Hear a bang, people screaming, running etc